Add task states

[emptybutton]

For each task, you need to make two buttons for entering/exiting states:

1. done
2. failed

Tasks can be in both done and failed states at the same time. If a task is not in one of the above states, then it is in the active state.

If only the done state is active, then the task should be recolored with a green accent. If only failed, then in red. If both states are active, then the entire left side of the task should be recolored as if it were only failed, and the right side as if it were only done.

If the task is active, then it should be purple as it is now by default.